How To Apply Chemistry to Cosmetology


The cosmetology industry is based on the use of chemicals and chemical compounds. Hair color, rinses, perms, chemical hair relaxers, shampoos, conditioners, and ingredients used in cosmetics and other skin care products commonly all contain chemicals. In order not to cause damage to a client's hair or skin, it is necessary for a cosmetologist to know what ingredients are contained in the products she or he uses, as well as be familiar with any chemical reactions those products may create.

  • Determine the effects of chemicals on the hair. How shampoos and conditioners work is based on chemistry. Surfactant molecules, or the cleansing agent in shampoo, attract water at one end and oil at the other end. This helps to wash away dirty sebum at the hair's roots. Ingredients in shampoo also replace the sebum stripped away by shampooing.

  • Chemicals can change hair texture. For example, perms are used to make straight hair wavy or curly. Perm solutions soften hair, allowing it to take on a new shape. Sulfur atoms connect to each other, forming disulfide bonds. Since curly hair has more disulfide bonds, perm solutions work by chemically increasing the number of those bonds in straight hair.

  • Use hair-straightening products to make curly hair straight. This process makes chemical changes to the hair by rearranging the structure of the hair. Hair relaxers break disulfide bonds allowing the hydrogen bonds in hair to reform and take on a flat shape.

  • Change hair color. Hair coloring techniques can alter the color of hair either temporarily or permanently by adding or removing pigment. Chemicals are used to change the color of the outer part of the hair shaft. When ingredients in the hair dye combine with oxygen, a chemical reaction occurs that binds the new hair color to the hair shaft. The chemical ingredients in permanent hair dyes actually strip the hair of its natural color. Once the natural pigment is dissolved, hair dye can then penetrate through the outer layer of hair into the hair pigment molecules.

  • Match pH levels before selecting shampoo and hair color. Hair is normally acidic, but shampoos and other hair care products can leave it alkaline. Products that have a higher pH rating are more alkaline, and therefore, can leave hair dry and brittle. When reacting with water, an alkaline shampoo can break disulfide bonds causing split ends.

Tips & Warnings

  • Eugene Schueller, a French chemist, created the first commercial hair dye in 1907. That hair dye became the mainstay product for the company known as L'Oreal. Today most hair color products still contain those same chemical compounds. Make certain that the hair is left in a healthy condition following chemical treatments which can damage the hair's natural moisture. Always rinse hair thoroughly for three minutes following any chemical treatment. Use clean, warm water, squeezing out any excess.

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